The present invention relates to hands-free adapters for cellular telephones, and in particular to a hands-free adapter which is compact in size and which has adequate loudspeaker and microphone capacities but which reduces the negative effects of howling or feedback.
Cellular telephone usage has risen dramatically over recent years and will probably continue to rise in the future. Widespread availability and affordability of cellular telephones is affecting the way people conduct business and communicate socially. Cellular telephones are so useful they have become practically a necessity to many professionals and highly desirable for social use in a wide variety of circumstances. People now use cellular telephones while driving in their cars, walking down the street, relaxing outdoors, etc.
In spite of the great utility and convenience of cellular telephones, their manner of use presents some difficulties, inconveniences, and even dangers. Typical use of a cellular telephone generally requires that the user hold the cellular telephone against the side of the user's head, so that microphone is extremely close to the user's mouth, and so that the speaker is extremely close to the user's ear. This generally requires the constant use of at least one of the user's hands, which is often inconvenient and can be dangerous, for example, when driving a car. Further, many people find it uncomfortable and annoying to have a cellular telephone up against their face during conversation. In addition, there is concern that the proximity of the cellular telephone to the user's head may present health dangers from exposure to microwave radiation.
The increasing amount of time that a typical user spends using a cellular telephone and the increasing variety of circumstances in which cellular telephones are used have made practical and convenient hands free cellular telephone usage greatly desirable. One approach to handling this problem has been to provide hands free headset devices worn on the user's head, including a set of earphones and a microphone situated close to the users mouth, which devices connect to the user's cellular telephone. There are a number of problems with the hands free head set device approach, however. Headsets can be uncomfortable, unattractive, cumbersome and annoying to wear. In addition, the user must remove the headset to perform various activities such as to eat, or to engage in normal physical interaction with other people.
Another approach to the problem has been aimed at providing speakerphone devices. Typical speakerphone devices can be useful in the context of wired telephones and cordless telephones, when a large speakerphone can be left in one place and used by a user who remains in the area near the speakerphone device. Of course, such large speakerphone devices are not conveniently portable, so their use with cellular telephones would to a large extent defeat an important purpose of the cellular telephone in serving as a portable communications device.
For these reasons, much effort of late has been directed to providing a conveniently portable speakerphone device adaptable for use with a cellular telephone. One approach, for users of cellular telephones in cars, has been to provide devices that connect with a cellular telephone to allow loudspeaker broadcast of incoming voice sound, such as though the speakers of the car's stereo system, and to provide a hands free microphone that extends near the driver's mouth.
A greatly desirable solution, however, for a wide variety of circumstances of cellular telephone usage, would be to provide a small, light, conveniently portable device that a user could connect to the user's cellular telephone to provide convenient hands free speakerphone operation. Such a solution would allow a user to simultaneously enjoy the benefits of the portable communications capability of a cellular telephone as well as the more natural, convenient and safe method of communication of a speakerphone device.
In spite of the desirability of such a solution, however, implementation has proved difficult to achieve. One problem is that speakerphone devices have an inherent difficulty in that the loudspeaker broadcast of incoming voice sound tends to be picked up by the microphone which is intended to pick up the voice of the person physically near the speakerphone. The microphone can pick up these broadcast signals not only outside the device but also inside the device, especially if the device is compact. This causes sound problems, such as echoing and feedback type problems, for users of speakerphone devices, which problems are sometimes referred to as “howling”. The howling problem becomes more severe when the microphone is situated very close to the speaker, such as would need to be the case in a small, portable speakerphone device. This applies particularly for internal howling.
One way to reduce howling includes reducing the sensitivity of the microphone or volume of the speaker. However, it then becomes more difficult for the user or the individual with whom the user is speaking to hear and understand each other. To mitigate less severe howling problems that occur with large speakerphone devices, circuitry known as attenuation circuitry has been used, which may vary the level of amplification of the signal provided to the microphone or the output power of the loudspeaker, to reduce howling. However, attenuation circuitry has no or little effect on internal howling.
Thus, despite the availability of the above methods of mitigating howling in speakerphone devices, attempts to design a speakerphone device small enough to be conveniently portable and in which howling is satisfactorily mitigated have in the past proved unsuccessful.
A conveniently compact and portable speakerphone device adaptable for use with a cellular telephone would enable the user to enjoy hands and headset free operation of the user's cellular telephone practically anywhere and during all kinds of activities, from driving in a car to sitting on bench to lying on a blanket.
Therefore, there is a need in the art for a portable hands-free or speakerphone device adaptable for use with a cellular telephone.